The present invention provides an addressing protocol for use in a wireless computer network in which a subscriber is assigned a network address based upon an original location in the network. As the subscriber moves throughout the network, data for the subscriber is routed to a cell site server at the subscriber's original location. The cell site server determines whether the subscriber is located in the original cell site, in which case it causes the data to be transmitted to the subscriber over a wireless link, or whether the subscriber has moved to a location serviced by a second cell site server. In the latter case, the first cell site server causes the data to be tunneled to the second cell site server.
To connect to the Internet, every terminal requires an Internet Protocol (IP) address that uniquely identifies the node's point of attachment to the Internet. In other words, a node must be located on the network as indicated by its IP address to receive data destined to it; otherwise, data destined to the node would be undeliverable. IP network address allocation and administration have historically assumed that there is a close relationship between a computer's IP address and its physical location.
In a wireless communication network, however, a subscriber can travel between various cells, thereby receiving transmissions from a variety of base stations. The transmissions are handed off from one base station to another as the subscriber travels from one cell to another. If such a system were to be attempted for Internet routing, when a terminal connects to the Internet while in a particular cell, the base station in that cell connects to a server that provides the IP address for the mobile unit. As the terminal moves through the geography and approaches another base station, a handoff is performed. That is, the transmission between the terminal and the base station is handed off to another base station. This other base station is now responsible for routing data packets.
Of course, moving across a network creates addressing problems that are peculiar to the mobile environment. Specifically, as a terminal moves from point to point on a network, the network must somehow know where the terminal is located so that data packets can be delivered to the terminal. If the terminal requests data in one cell, for example, and travels to another cell, the network must know the terminal's present location so that data packets can be accurately delivered. Unfortunately, because a base station in a first cell may not be in direct communication with a base station in a second cell, traffic can be lost during a handoff. Thus, when a handoff occurs, a terminal's connection to the Internet can get dropped because the new base station does not know the terminal's IP address for data exchange with the Internet.
To account for this addressing problem in the current art, if one connects to the Internet in a mobile environment, a technique called Mobile IP is used. This Mobile IP is a modification to IP that allows nodes to continue to receive data no matter where they happen to be attached to the Internet.
Internet nodes typically use the IP address of a destination node when searching for connections to that destination. Thus, the IP address of a remote endpoint also serves to identify the endpoint. For mobile computers, a destination network is known as the home network. Since the mobile node appears to the rest of the Internet as if it were actually located on the home network, it can be called the home address of the mobile node. If the source of the packet is assumed to be an Internet node with no special modification for mobility support, the source will be unaware whether anything special happens when a packet arrives at the home network.
If, however, the mobile node is not directly attached to its home network, then the packet requires a “care of” address to find the next node. Because the packet can only follow the mobile node by utilizing the existing Internet infrastructure for the intervening hops, Mobile IP changes the data's address scheme so that a packet is able to follow the mobile node off the home network. This operation of changing the address of the packet for further routing is known as readdressing. The operation of readdressing a packet transforms its original destination IP address, the home address that identifies the mobile node, into a different destination IP address, namely, the care-of address, which locates the mobile node.
Additionally, for supporting mobility, the inverse of the readdressing function must be performed. That is, if one agent applies an address translation function to a packet destined for a mobile node, the inverse function should be provided so that the nodes with which it corresponds can operate in a symmetrical manner. Otherwise, the mobile node's home address, identifying the higher-level protocol connection status control blocks, would not be available in the same way as expected by the node that originally sent the packet. Typically, higher-level protocols do operate in this symmetric fashion.
The care-of address is used in lieu of an IP address, but requires a new set of protocols and modifications to the existing network stack.
Because of the need for a care-of address, a central location must be maintained that collects all traffic to be forwarded. Additionally, modifications must be made to network components and the existing network stack. Furthermore, a new set of protocols are required to employ Mobile IP. None of these alternatives are optimal, given the severe scaling problems that are especially relevant considering the explosive growth in mobile computers.
Thus, a need exists in the current state of the art for a mobile network that does not require substantial modifications to the existing network components and protocols.